A Falcon 9 rocket rolls out to pad 39A Thursday for the next launch of SpaceX Starlink satellites. Credit: Spaceflight Now

SpaceX plans to deploy the next group of Starlink internet relay spacecraft Sunday with a liftoff on top of a Falcon 9 rocket from NASAs Kennedy Space Center, the companys fourth satellite launch of the month.

The two-stage Falcon 9 launcher emerged from its hangar at the Florida spaceport Thursday and rolled up the ramp to pad 39A, where SpaceX will raise the 229-foot-tall (70-meter) rocket vertical for a test-firing as soon as Friday.

The hold-down firing of the rockets nine Merlin 1D main engines will last several seconds.

The test, which SpaceX calls a static fire, was part of every Falcon 9 launch campaign for nearly a decade. But SpaceX did not perform a static fire before its last four missions as teams try to cut the time required between Falcon 9 flights from SpaceXs two launch pads on Floridas Space Coast.

Assuming a good test-firing Friday, SpaceX is expected to press ahead with launch of the Falcon 9 rocket Sunday. There is an instantaneous launch opportunity at 7:02 a.m. EST (1202 GMT), about 10 minutes before sunrise Sunday.

The Falcon 9 will launch with the next batch of approximately 60 Starlink satellites, adding more capacity and coverage to SpaceXs burgeoning broadband network.

Warning notices to pilots and mariners previously indicated the launch was scheduled Saturday morning, but sources said Thursday the flight was delayed to Sunday.

Forecasters from the U.S. Space Forces 45th Weather Squadron predict an 80% chance of good weather Sunday. The primary weather concern Sunday will be with the possibility of violating the cumulus cloud rule.

A high pressure ridge is forecast to begin moving away from Central Florida this weekend, allowing a low pressure system and a cold front to move into the Mid-Atlantic states north of Florida.

The spaceport will be within the warm, prefrontal regime during the launch window, the weather team wrote Thursday. Clouds will be thicker and more abundant than Saturday, but the vast majority will be too low-topped to create lightning launch commit criteria concerns. Southwesterly winds will increase to 15-20 miles per hour (up to 200 feet) in response to the tightening pressure gradient. The primary concern during the backup window will be the cumulus cloud rule.

If the Starlink mission takes off Sunday, SpaceX will close out January with four Falcon 9 launches, keeping pace with the companys goal of launching more than 40 Falcon flights in 2021.

A Falcon 9 rocket took off Jan. 7 from pad 40 at Cape Canaveral Space Force Station with the Turkish-owned Turksat 5A communications satellite. SpaceX launched 60 Starlink satellites Jan. 20 from pad 39A, then launched a rideshare mission Sunday on a Falcon 9 with a record-setting payload of 143 small satellites from U.S. and international customers.

SpaceX, founded and led by billionaire Elon Musk, will have more than 1,000 Starlink nodes in orbit with the roughly 60 more Starlink spacecraft set to launch Sunday. The company has launched 1,025 Starlink satellites to date, but some of the spacecraft were either prototypes or failed after launch, and are no longer in orbit, according to Jonathan McDowell, an astronomerat theHarvard-Smithsonian Center for Astrophysics who tracks global satellite and launch activity.

SpaceX says the Starlink network is providing preliminary low-latency internet service to users in the United States, Canada, and the United Kingdom through a beta testing program. Commercial service will begin after SpaceX has its initial network of around 1,584 satellites in orbit, including spares.

The quarter-ton Starlink satellites are built by SpaceX technicians and engineers in Redmond, Washington.

The initial block of Starlink satellites, including the 60 launching this weekend, fly in mid-inclination orbits tilted 53 degrees to the equator. They fly at an altitude of 341 miles, or 550 kilometers, to provide broadband coverage over nearly all of the populated world.

SpaceX plans to launch more Starlink satellites into polar orbit to enable global coverage for maritime and aviation customers, including the U.S. military. The company has regulatory approval to launch around 12,000 Starlink satellites.

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Falcon 9 rocket arrives on pad 39A for sunrise Starlink launch this weekend Spaceflight Now - Spaceflight Now